Short idea (130): "2 plus 2 = 4" may express an eternal truth, but adding 2 plus 2 is a mental operation that takes place in particular people at particular places and times. Thinking is an activity that uses up time, and it always occurs in a particular place. Thinking can be done out-loud or to oneself, with others or alone, while awake or while dreaming. Like all other activities, we think for reasons, and these reasons can be more or less conscious. And we can think too much or too little, and in a useful way or in a way that causes trouble for ourselves and/or others.